1. Field of the Invention
The present invention relates to silicon nitride bodies favorably usable as high temperature structural materials, and to a process for producing the same.
2. Related Art Statement
Various ceramic materials have been used as high temperature structural materials. High strength and high fracture toughness as well as good thermal shock resistance are cited as characteristics required for high temperature structural ceramics. High heat conductivity, low coefficient of thermal expansion, low Young's modulus, etc. are required to improve the thermal shock resistance. BeO, AlN, SiC, etc. have been heretofore known as ceramic materials having high thermal conductivity.
However, among the above-mentioned ceramic materials having high thermal conductivity, BeO and AlN have low strength, and SiC has high strength, but its fracture toughness is low.
On the other hand, although Si.sub.3 N.sub.4 is known as a material having high strength and high toughness, it generally has low thermal conductivity. Accordingly, hereto known silicon nitride sintered bodies have a problem in thermal shock resistance.